Substitute Mariano Izco escaped three minutes from time to hammer the final nail in Juve's coffin on a dreadful day for Ciro Ferrara's team yesterday, in which their fans once again chanted racist slogans.
That loss was compounded later in the day when league leaders Inter Milan beat Lazio 1-0 at the San Siro to open up a nine-point gap over Juve heading into the winter break.
AC Milan remained second, eight points behind Inter, despite their game at Fiorentina on Saturday being called off due to the weather.
Ferrara's side came into yesterday's match with four defeats from their last five games in all competitions, and with goalkeeper Gianluigi Buffon and defensive rock Giorgio Chiellini both out injured.
"I feel the same disappointment as the fans. We're going through a bad period, we're not getting the results expected of this team so of course I'm not happy," said Ferrara.
"We wanted to react and we fought for 90 minutes but we made some mistakes in our finishing. It's a tough time but we have to stick together if we are to get through the storm."
After surviving an early penalty scare as Japanese forward Takayuki Morimoto went down under a challenge from Nicola Legrottaglie, Tiago then gave one away as he tugged Nicolas Spolli's shirt in the box.
Jorge Martinez made the hosts pay as he stroked home the penalty.
Even that failed to spark much life into Juve and on 32 minutes, Ferrara had seen enough and hauled off 20-million-euro Brazilian flop Felipe Melo, throwing on Bosnian veteran Hasan Salihamidzic in his place, with Melo roundly jeered as he trooped off.
"Felipe, like other players, was not playing well and making too many mistakes so I decided to substitute him," explained Ferrara.
Juve were lively at the start of the second period with Diego, another expensive signing who has failed to live up to his billing, shooting over before Amauri shot straight at goalkeeper Mariano Andujar and Salihamidzic sent an effort inches wide of the far post.
However, the Bosnian drew Juve level on 66 minutes when a delightful ball over the top from Diego found him free behind a static defence and he turned smartly to shoot under Andujar.
Andujar spread himself to deny David Trezeguet with a quarter of an hour left and as Juve pilled on the pressure, Catania hit them with a rapier counter-attack, with Gianvito Plasmati releasing Izco to beat Alex Manniger.
Worse may be yet to come for Juve as some Ultras chanted "there are no black Italians" during the first half -- the same chant that saw Juve forced to play a game behind closed doors last season.
Struggling Lazio put up little fight against Inter and the only surprise was that the champions did not manage to score more goals.
Samuel Eto'o scored the only one in 14th minute at the second attempt after Dejan Stankovic found him with a cross, also at the second attempt.
Fernando Muslera saved Eto'o's header but the ball fell kindly to the Cameroon striker to lash home past the grounded goalkeeper.
For Lazio it was the 10th game in a row their strikers have failed to hit the net, but Inter boss Jose Mourinho said this time it was due to how his team played.
"We managed the game well, we scored and then we controlled the game and had chances for a second," he said.
"Lazio's problems in front of goal are nothing to do with me, what interests me is how we controlled the game for 90 minutes. It's three important points given that Juve got none and Milan didn't play."
In other games, Napoli beat Chievo 2-0 at home to extend their unbeaten run to 11 games since coach Walter Mazzarri replaced former Italy boss Roberto Donadoni in early October.
Roma leapfrogged Parma to go fourth after beating the promoted side 2-0 in the capital.
There were protests at lowly Livorno against the club's owners and the game was held up for two minutes due to smoke bombs before the hosts beat free-falling Sampdoria 3-1.
